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Use of NH4F and High pH, Buffered HF Acid Solutions for Precleaning Silicon (100) Wafers Prior to Low Temperature Epitaxy

IP.com Disclosure Number: IPCOM000122458D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 48K

Publishing Venue

IBM

Related People

Ronsheim, PA: AUTHOR [+2]

Abstract

This article describes the use of NH4F solutions with a pH of about 8.0 and buffered HF acid solutions with a high pH, i.e., greater than 7.0, to preclean silicon (100) wafers prior to low temperature epitaxy, e.g., by UHVCVD.

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Use of NH4F and High pH, Buffered HF Acid Solutions for Precleaning
Silicon (100) Wafers Prior to Low Temperature Epitaxy

      This article describes the use of NH4F solutions with a
pH of about 8.0 and buffered HF acid solutions with a high pH, i.e.,
greater than 7.0, to preclean silicon (100) wafers prior to low
temperature epitaxy, e.g., by UHVCVD.

      The conventional ex-situ precleaning process for UHVCVD
consists of the etching of the surface oxides on the silicon
substrates by dilute HF solutions with a pH between 1.0 and 2.0,
without a subsequent water rinse.  This etching process results in a
silicon surface passivated by hydrogen termination [1,2,3].  The
hydrogen termination is multimodal consisting of monohydride,
dihydride and trihydride phases. Furthermore, the hydrogen
termination is incomplete due to the presence of other chemical
species such as fluorine on the silicon surface.  Typically, some
residual oxygen is found at the interface after epitaxial growth on
silicon (100) substrates precleaned using this conventional etch.

      The multimodal nature of the hydrogen persists for Si (100)
surfaces treated with high pH, buffered HF etches [4]. However, the
quality of the hydrogen passivation is considerably improved, as
evidenced by reduced amounts of interfacial oxygen observed after
epitaxy on silicon (100) surfaces etched with either NH4F solutions
a pH of about 8.0, or buffered HF solutions with a pH greater than
7.0.

      The...